Carbonyl difluoride is an attractive and important compound as a semiconductor etching gas or a semiconductor cleaning gas. For example, known processes for producing carbonyl difluoride are described in the following patent literatures.
(1) WO 05/56472 (Patent Literature 1) discloses a process wherein carbon monoxide and fluorine gas together with hydrogen fluoride or carbonyl difluoride as a diluting gas are continuously supplied to a reaction vessel and are reacted together to produce carbonyl difluoride.
(2) JP-A-2004-262679 (Patent Literature 2) discloses a process for the production of carbonyl difluoride including the following first step and second step:
First step: Phosgene (COCl2) and hydrogen fluoride are reacted to give a mixture of carbonyl difluoride, chlorofluorocarbonyl (COClF) and hydrogen chloride, and the mixture is distilled to remove carbonyl difluoride and hydrogen chloride, thereby obtaining chlorofluorocarbonyl.
Second step: Chlorofluorocarbonyl obtained in the first step is subjected to disproportionation reaction to give a reaction mixture, and phosgene and chlorofluorocarbonyl are removed from the mixture to recover carbonyl difluoride.
(3) Japanese Patent No. 3707917 (Patent Literature 3) discloses a process for producing carbonyl difluoride by reacting carbon dioxide and fluorine gas in a gas phase.
(4) JP-A-2003-146620 (Patent Literature 4) discloses a process of producing carbonyl difluoride by reacting carbon monoxide and a metal fluoride (MFx: M is for example Co (x=2) or Ce (x=4)), wherein a step of reacting carbon monoxide and the metal fluoride, and a step of reacting the metal fluoride and fluorine are alternately repeated in a single reaction vessel.
(5) U.S. Pat. No. 2,836,622 (Patent Literature 5) discloses a process for the preparation of carbonyl difluoride including the following steps:
(i) a step in which phosgene is reacted with hydrogen fluoride at a temperature of at least 50° C. in the presence of, for example, an activated carbon catalyst to give a reaction product containing carbonyl difluoride and hydrogen chloride; and
(ii) a step in which the reaction product is brought into contact at temperatures above 0° C. with a stoichiometric amount, based on hydrogen chloride and unreacted hydrogen fluoride in the reaction product, of an inorganic compound (for example an alkali metal fluoride or sulfur trioxide) until substantially all of the hydrogen chloride and the hydrogen fluoride are absorbed.